1. Field of the Invention
The present invention relates to refill kits. More specifically, the present invention relates to a refill kit for an implantable pump having a fluid reservoir under high pressure.
2. Discussion of the Related Art
The implantable drug infusion pump (IDIP) has provided physicians with a powerful tool for administering a wide variety of drugs and other agents, such as pain killers, nerve growth factor, and anti-spasticity drugs, to very particularized sites within a patient's body, such as the intrathecal region of the spinal column. The IDIP has also freed some patients from the restrictions of typical intravenous drug infusion systems that typically include a wheeled cart that must be pulled around behind the patient.
An IDIP is ordinarily surgically implanted subcutaneously in the patient's abdomen. The IDIP has an internal reservoir for storing the drug or agent. After implantation, the drug or agent is delivered to a selected site in the patient's body via a catheter that is attached to the pump and tunneled subcutaneously to the selected site.
Before the IDIP can be implanted in the patient's body, it must be filled with the applicable drug or agent. For many long-term applications, the IDIP may have to be refilled while the pump is still implanted within the patient's body. This is normally done by passing the drug or agent through a hypodermic needle that has been pierced through the patient's skin and coupled to the subcutaneously disposed IDIP. However, before refilling the IDIP, any remaining drug or agent contained within the reservoir must first be emptied. Typically, the IDIP is emptied by simply connecting the filling needle to a collection syringe. Thereafter, the collection syringe is disconnected from the tube connected to the filling needle. The IDIP is then refilled in a conventional manner.
In an IDIP, a propellant gas is placed in a pressure chamber to apply a pressure to a reservoir that receives the drug or agent. The reservoir is typically defined by a bellows structure so that the volume of the reservoir may vary. The propellant gas acts as a pressure-providing means to the bellows structure that biases the bellows structure to discharge the drug or other agent stored in the reservoir. The propellant gas used to drive such a “gas driven” IDIP is a fluid that is in phase change between a liquid state and a gas state when, i.e., in equilibrium between phases at around 37 degrees (Celsius), which is the usual temperature of the human body. In IDIPs, the propellant gas is chosen to provide a pressure on the bellows structure of about 9 p.s.i. to about 36 p.s.i.
As mentioned above, when refilling the IDIP, the drug or other agent is passed from a syringe into the IDIP, where it enters into the reservoir. However, the drug or other agent must enter the reservoir at a pressure sufficient to overcome the pressure bias on the reservoir from the propellant gas in the pressure chamber. In some cases, the drug or other agent must be delivered to the reservoir at a pressure higher than 36 p.s.i.
Due to the principles of hydraulics, this 36 p.s.i. pressure is applied over the entire cross-sectional area of the plunger within the syringe. When refilling an IDIP, typically the entire reservoir capacity of the IDIP is refilled. A typical IDIP may have a reservoir volume of 20 ml, 40 ml or 50 ml. To refill an IDIP with, for example, a 50 ml reservoir, a pharmacy typically prepares 50 ml of the drug or other agent and places it in a pharmacy syringe corresponding in size to the amount of drug or other agent to be refilled, in this case, a 50 ml syringe. The 50 ml pharmacy syringe could be coupled directly to the IDIP.
As is well known, the cross-sectional area of the plunger of a relatively small syringe such as a 10 ml syringe is smaller than the cross-sectional area of a larger syringe such as a 50 ml syringe. As a result, the force needed to apply 36 p.s.i. to drug or other agent in a syringe is determined by multiplying 36 p.s.i. by the cross-sectional area of the plunger. In the case of a 50 ml syringe, this total force is on the order of 25 pounds. This is a larger force than many people are able to generate with their hands. On the other hand, because the cross-sectional area of a 10 ml syringe is substantially smaller than the cross-sectional area of a 50 ml syringe, the total force needed to apply apply 36 p.s.i. to drug or other agent in a 10 ml syringe is about 6 pounds. This force is well within the range of force that most people can generate with their hands.
As a result, many practitioners, when refilling large reservoir pumps such as the 50 ml reservoir pumps, require the pharmacy to place the 50 ml of the drug or other agent to be refilled into several smaller syringes such as 10 or 20 ml syringes instead of in one large syringe. These smaller syringes allow the practitioner to apply the drug or other agent to the reservoir even in pumps that have relatively high gas propellant pressures in their pressure chambers. Unfortunately, using several smaller syringes instead of one large syringe means that each syringe must be attached and disconnected from the inlet each time instead of once as would be the case for the larger syringe. With this increased number of connections and disconnections, there is an increased chance of infection entering the system or other problems occurring.
U.S. Pat. No. 6,360,784 to Philippens et al. discloses a valved connector that solves some of these problems by providing a system that allows the practitioner to provide the drug or other agent to the reservoir of the IDIP while minimizing the number of times the sterile connection between the pharmacy syringe and the system is broken. But Philippens requires the application of a manual clamp in the filling tube line which must be opened and closed at specific times during the refilling cycle to permit Philippens' system to operate properly. Also, Philippens' incorporates a one-way valve 60 in a connector that must be located in a central lumen between the first inlet port from the first syringe and a point where the second inlet port from the second syringe connects to the central lumen. The one-way valve is biased to allow fluid to pass only from the first inlet port to the central lumen, and never from the second inlet port to the first inlet port.
In view of the foregoing, it is desirable to provide a system that allows the practitioner to easily empty the reservoir and thereafter provide the drug or other agent to the reservoir of the IDIP. The present invention is directed to overcoming the aforementioned disadvantages.